/*
 * Copyright 2017-present Facebook, Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License"); you may
 * not use this file except in compliance with the License. You may obtain
 * a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
 * License for the specific language governing permissions and limitations
 * under the License.
 */

package com.facebook.buck.jvm.java.abi.source;

import com.facebook.buck.jvm.java.plugin.adapter.BuckJavacPlugin;
import com.facebook.buck.jvm.java.plugin.adapter.BuckJavacTask;
import com.sun.source.util.TaskEvent;
import com.sun.source.util.TaskListener;

/**
 * Watches the phases of the compiler and keeps our parallel symbol table in sync. Put task
 * listeners that need access to our symbol tables inside this one.
 */
class EnteringPlugin implements BuckJavacPlugin {
  @Override
  public String getName() {
    return "EnteringPlugin";
  }

  @Override
  public void init(BuckJavacTask task, String... args) {
    FrontendOnlyJavacTask frontendTask = (FrontendOnlyJavacTask) task;
    task.addTaskListener(
        new EnteringTaskListener(frontendTask.getElements(), frontendTask.getTrees()));
  }

  private static class EnteringTaskListener implements TaskListener {
    private final TreeBackedElements elements;
    private final TreeBackedTrees trees;
    private final TreeBackedEnter enter;
    private int classesEnteredThisRound = 0;

    public EnteringTaskListener(TreeBackedElements elements, TreeBackedTrees trees) {
      this.elements = elements;
      this.trees = trees;
      enter = new TreeBackedEnter(this.elements, this.trees);
    }

    @Override
    public void started(TaskEvent e) {
      if (e.getKind() == TaskEvent.Kind.ENTER && classesEnteredThisRound == 0) {
        // We want to clear our tables between rounds, and leave them intact after the last enter
        // phase. However, javac sends the round start after the enter phase, so we must do some
        // bookkeeping to detect the first enter event *after* a round and clear the table then.
        elements.clear();
        trees.clear();
      }
    }

    @Override
    public void finished(TaskEvent e) {
      if (e.getKind() == TaskEvent.Kind.ENTER) {
        enter.enter(e.getCompilationUnit());
        classesEnteredThisRound += 1;
      } else if (e.getKind() == TaskEvent.Kind.ANNOTATION_PROCESSING_ROUND) {
        // Reset counter for next round
        classesEnteredThisRound = 0;
      }
    }
  }
}